"We have no idea why these events are occurring," police official says

For the 23rd and 24th time in less than two weeks, shots were fired at seemingly random targets in southeastern Michigan and, for the first time, someone was struck, police said.

A driver suffered non-life-threatening injuries, details of which were not disclosed, when he was hit by a bullet around 12:20 p.m. ET west of Fowlerville, said Clarence Goodlein, director of public safety in Wixom and spokesman for the eight-agency task force investigating the shootings.

After that incident -- which occurred about 35 minutes after another shooting, both affecting vehicles heading eastbound on Interstate 96 -- authorities shut down the highway, looking for evidence.

It reopened shortly after 5 p.m., without anyone in custody or a named suspect.

Michigan authorities have released a composite sketch of a man with short-cropped hair who they believe was involved in an October 18 shooting in Ingham County.

And police have said they are looking for a black Ford Mustang with blue-tinted front lights and a racing stripe down the center, while other witnesses have pointed to an older-model Chevrolet Cavalier.

Saturday's highway shootings are the latest in a series that began October 16 in Wixom and a neighboring community. They have all occurred over a roughly 35-mile stretch west of Detroit.

Goodlein said authorities have indications the suspect or suspects were themselves in vehicles when they fired at other vehicles that were driving in the opposite direction. What would motivate them to do so, however, is a mystery.

"We have no idea why these events are occurring," Goodlein said.

In one of the shootings, a man taking out his trash heard a bullet "whizzing by his head, Oakland County Sheriff Michael Bouchard said earlier this month. In another, a bullet went through the driver's side of a car, lodging inside the passenger-side door. And on one day, five vehicles were shot along the same road in a span of "two to three minutes," according to Goodlein.

"The scariest thing about it is the suspect, or suspects, are not targeting certain individuals," said Brian Cheesvro, a detective with the Wixom police.

The incidents have stirred memories of the D.C. sniper shootings, when 10 were killed and three wounded over a terrifying three-week span in October 2002. John Allen Muhammad, the mastermind behind those shootings, was found guilty and executed in 2009. Lee Boyd Malvo, who was 17 at the time, is serving a life sentence.

Over the past two weeks, dozens of law enforcement officers have come together to form a task force to probe the Michigan shootings.

Goodlein said about 500 leads have come in through a tip line, and he encouraged people to keep calling -- even if they are not sure whether their thoughts or observations will impact the investigation.

"Our experience has been ... that one piece of meaningless information, or what seems to be meaningless to someone, when it is combined with some other information ... becomes extremely valuable," the chief said.